1. Field of the Invention
The present invention relates to an apparatus and method for fabricating semiconductor devices, and more particularly, to a chemical-mechanical polishing (CMP) apparatus and method.
2. Background of the Related Art
As the integration of semiconductor devices increases, multi-level interconnection technology has been put into practical use. Accordingly, local and global planarization of interlayer dielectric films has become important. Currently, a widely used CMP method of polishing the surface of a semiconductor wafer employs chemical components contained in a slurry solution, mechanical components of a polishing pad, and a polishing agent.
A CMP apparatus is mainly used in polishing the front face of a semiconductor wafer while fabricating semiconductor devices on the wafer. In general, in order to make the surface of the wafer as flat as possible, the wafer is planarized or softened at least one time during the fabrication process. In order to polish the wafer, the wafer is placed on a carrier, put into contact with the polishing pad covered with slurry and then pressed. While polishing is carried out, both the polishing pad and the wafer-loaded carrier rotate.
After polishing is carried out, the carrier moves upward so that the wafer is completely separated from the polishing pad. In this case, deionized water remains between the wafer and the surface of the polishing pad. Due to the deionized water, a strong adsorptive force is produced on the contact surface between the wafer and the polishing pad. If the carrier is raised in the presence of the adsorptive force, the wafer may separate from the carrier and remain fixed on the polishing pad. In such an event, subsequent processes would not be performed, and damage to the wafer may be caused.
To solve the above problems, it is an object of the present invention to provide a chemical-mechanical polishing (CMP) apparatus and method, by which a wafer stays on the carrier when the wafer-loaded carrier separates from the polishing pad after polishing is completed.
Accordingly, the present invention provides a CMP apparatus having a polishing pad covered with slurry, and a polishing head fixed on a semiconductor wafer for holding the surface of the semiconductor wafer in contact with the surface of the polishing pad, wherein the polishing head includes a wafer carrier on which the semiconductor wafer is fixed, and a retainer ring formed along the wafer carrier so as to guide the edges of the semiconductor wafer. The retainer ring has an opening through which air is supplied to the lower portion thereof, so that air is injected between the semiconductor wafer and the polishing pad through the opening before separating the semiconductor wafer from the polishing pad after the polishing process.
It is preferred that the opening is close to the semiconductor wafer and the opening is connected to an air injection opening formed in a shaft for supporting the polishing head and the rotary shaft of the polishing head. Also, the opening may vertically penetrate the inside of the retainer ring.
Also, the CMP apparatus may further include a sensor for sensing whether the semiconductor wafer is adhered to the wafer carrier after separating the wafer carrier from the polishing pad.
The present invention further provides a CMP method in which the polishing head moves upward so that the semiconductor wafer is separated from the polishing pad after polishing is complete, while the adsorptive force between the semiconductor wafer and the polishing pad is reduced by injecting air therebetween through the opening.
Here, the CMP method may further include sensing whether or not the semiconductor wafer is adhered to the polishing head after the polishing head is separated from the polishing pad, and displaying the sensing result to a user.